CN110262020B - Zoom lens and optical apparatus - Google Patents

Abstract

The invention provides a zoom lens and an optical apparatus. The zoom lens includes a 1 st lens group having positive power, a2 nd lens group having negative power, a 3 rd lens group having positive power, a 4 th lens group having negative power, and a 5 th lens group having positive power, which are arranged in order from an object side along an optical axis, the 1 st lens group, the 2 nd lens group, the 3 rd lens group, the 4 th lens group, and the 5 th lens group moving along the optical axis in such a manner that an interval between the 1 st lens group and the 2 nd lens group, an interval between the 2 nd lens group and the 3 rd lens group, an interval between the 3 rd lens group and the 4 th lens group, and an interval between the 4 th lens group and the 5 th lens group vary, respectively, when zooming from a wide-angle end state to a telephoto end state, the 2 nd lens group is composed of a 1 st negative lens, a2 nd negative lens, a positive lens, and a 3 rd negative lens group, the positive lens and the 3 rd negative lens are cemented.

Description

Zoom lens and optical apparatus

The present application is a divisional application of an invention patent application having an international application date of 2014-11-21, an international application number of PCT/JP2014/005861, a national application number of 201480070381.9, and an invention name of "zoom lens and optical device".

Technical Field

The invention relates to a zoom lens, an optical apparatus, and a method of manufacturing the zoom lens.

Background

Conventionally, various zoom lenses having a large zoom ratio, which are applicable to a camera for photography, an electronic still camera, a video camera, and the like, have been disclosed (for example, see patent document 1).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2012 and 98699

Disclosure of Invention

Problems to be solved by the invention

However, in the conventional zoom lens, it is difficult to increase the magnification ratio while downsizing the entire optical system.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a zoom lens, an optical apparatus, and a method of manufacturing the zoom lens, which are small in size, have a large zoom ratio, and have good optical performance.

Means for solving the problems

1A zoom lens of the present invention includes, in order from an object side along an optical axis, a 1 st lens group having positive power, a2 nd lens group having negative power, a 3 rd lens group having positive power, a 4 th lens group having negative power, and a 5 th lens group having positive power, the 1 st lens group, the 2 nd lens group, the 3 rd lens group, the 4 th lens group, and the 5 th lens group move along an optical axis in a manner that an interval between the 1 st lens group and the 2 nd lens group, an interval between the 2 nd lens group and the 3 rd lens group, an interval between the 3 rd lens group and the 4 th lens group, and an interval between the 4 th lens group and the 5 th lens group vary, respectively, upon varying magnification from a wide-angle end state to a telephoto end state, and satisfy the following conditional expressions:

0.25<f1/ft<0.38

wherein,

f 1: a focal length of the 1 st lens group,

ft: and the focal length of the zoom lens in a far focus end state.

In the zoom lens according to claim 1, it is preferable that the following conditional expression is satisfied:

-0.180<(f1×fw)/(f2×ft)<-0.160

wherein,

fw: a focal length in a wide-angle end state of the zoom lens,

f 2: focal length of the 2 nd lens group.

In the zoom lens of claim 1, it is preferable that the 1 st lens group has three positive lenses.

In the zoom lens according to claim 1, it is preferable that the 1 st lens group has a cemented lens of a positive lens and a negative lens, and satisfies the following conditional expression:

0.367<nN1-nP1

80<νP1

wherein,

nN 1: a refractive index with respect to a d-line of the negative lens of the cemented lens constituting the 1 st lens group,

nP 1: a refractive index with respect to a d-line of the positive lens of the cemented lens constituting the 1 st lens group,

ν P1: abbe number of the positive lens of the cemented lens constituting the 1 st lens group.

In the zoom lens according to claim 1, it is preferable that the following conditional expression is satisfied:

-0.18<f4/ft<-0.14

wherein,

f 4: focal length of the 4 th lens group.

In the zoom lens of claim 1, it is preferable that the 4 th lens group is constituted by a cemented lens of one positive lens and one negative lens.

In the zoom lens according to claim 1, it is preferable that an aperture stop is disposed in the vicinity of the object side of the 3 rd lens group, and the following conditional expression is satisfied:

0.084<ΔZwt/ft<0.090

wherein,

Δ Zwt: a moving distance of the aperture stop to the object side on the optical axis at the time of varying magnification from the wide-angle end state to the telephoto end state.

The zoom lens according to the 2 nd aspect of the present invention includes, in order from the object side along the optical axis, a 1 st lens group having positive power, a2 nd lens group having negative power, a 3 rd lens group having positive power, a 4 th lens group having negative power, and a 5 th lens group having positive power, and when zooming from a wide-angle end state to a telephoto end state, the 1 st lens group, the 2 nd lens group, the 3 rd lens group, the 4 th lens group, and the 5 th lens group move along the optical axis such that an interval between the 1 st lens group and the 2 nd lens group, an interval between the 2 nd lens group and the 3 rd lens group, an interval between the 3 rd lens group and the 4 th lens group, and an interval between the 4 th lens group and the 5 th lens group respectively vary, and the 2 nd lens group is moved along the optical axis by the 1 st negative lens group, an interval between the 1 st lens group, a negative lens group, a third lens group, a fourth lens group, and a fourth lens group, each having positive power, A2 nd negative lens, a positive lens and a 3 rd negative lens, wherein the positive lens and the 3 rd negative lens are jointed.

In the zoom lens according to claim 2 of the present invention, it is preferable that the following conditional expression is satisfied:

-0.180<(f1×fw)/(f2×ft)<-0.160

wherein,

fw: a focal length in a wide-angle end state of the zoom lens,

ft: a focal length of the zoom lens in a far-focus end state,

f 1: a focal length of the 1 st lens group,

f 2: focal length of the 2 nd lens group.

In the zoom lens according to claim 2 of the present invention, it is preferable that the following conditional expression is satisfied:

-0.180<f4/ft<-0.140

wherein,

ft: a focal length of the zoom lens in a far-focus end state,

f 4: focal length of the 4 th lens group.

In the zoom lens of claim 2, it is preferable that the 4 th lens group is composed of a cemented lens of one positive lens and one negative lens.

The zoom lens of the 3 rd invention includes, in order from the object side along the optical axis, a 1 st lens group having positive power, a2 nd lens group having negative power, a 3 rd lens group having positive power, a 4 th lens group having negative power, and a 5 th lens group having positive power, the 1 st lens group, the 2 nd lens group, the 3 rd lens group, the 4 th lens group, and the 5 th lens group move along an optical axis in a manner that an interval between the 1 st lens group and the 2 nd lens group, an interval between the 2 nd lens group and the 3 rd lens group, an interval between the 3 rd lens group and the 4 th lens group, and an interval between the 4 th lens group and the 5 th lens group vary, respectively, upon varying magnification from a wide-angle end state to a telephoto end state, and satisfy the following conditional expressions:

-0.90<f2/TL2<-0.60

-0.180<f4/ft<-0.140

wherein,

f 2: a focal length of the 2 nd lens group,

TL 2: a length on the optical axis of the 2 nd lens group,

f 4: a focal length of the 4 th lens group,

ft: and the focal length of the zoom lens in a far focus end state.

In the zoom lens according to claim 3, it is preferable that the following conditional expression is satisfied:

-0.180<(f1×fw)/(f2×ft)<-0.160

wherein,

f 1: a focal length of the 1 st lens group,

fw: a focal length of the zoom lens in a wide-angle end state.

In the zoom lens of claim 3, it is preferable that the 4 th lens group is composed of a cemented lens of one positive lens and one negative lens.

The optical apparatus of the 1 st invention has a zoom lens for imaging an image of an object on a predetermined surface, and the zoom lens of the 1 st invention is used as the zoom lens. Similarly, the optical apparatus of the 2 nd invention has a zoom lens for forming an image of an object on a predetermined surface, and the zoom lens of the 2 nd invention is used as the zoom lens, and the optical apparatus of the 3 rd invention has a zoom lens for forming an image of an object on a predetermined surface, and the zoom lens of the 3 rd invention is used as the zoom lens.

A method of manufacturing a zoom lens according to the present invention includes disposing a 1 st lens group having positive power, a2 nd lens group having negative power, a 3 rd lens group having positive power, a 4 th lens group having negative power, and a 5 th lens group having positive power in this order from an object side along an optical axis, and moving the 1 st lens group, the 2 nd lens group, the 3 rd lens group, the 4 th lens group, and the 5 th lens group along the optical axis so that a distance between the 1 st lens group and the 2 nd lens group, a distance between the 2 nd lens group and the 3 rd lens group, a distance between the 3 rd lens group and the 4 th lens group, and a distance between the 4 th lens group and the 5 th lens group respectively change when zooming from a wide-angle end state to a telephoto end state, and satisfies the following conditional expressions:

0.25<f1/ft<0.38

wherein,

f 1: a focal length of the 1 st lens group,

ft: and the focal length of the zoom lens in a far focus end state.

A method of manufacturing a zoom lens according to the present invention includes disposing a 1 st lens group having positive power, a2 nd lens group having negative power, a 3 rd lens group having positive power, a 4 th lens group having negative power, and a 5 th lens group having positive power in this order from an object side along an optical axis, and moving the 1 st lens group, the 2 nd lens group, the 3 rd lens group, the 4 th lens group, and the 5 th lens group along the optical axis so that a distance between the 1 st lens group and the 2 nd lens group, a distance between the 2 nd lens group and the 3 rd lens group, a distance between the 3 rd lens group and the 4 th lens group, and a distance between the 4 th lens group and the 5 th lens group respectively change when zooming from a wide-angle end state to a telephoto end state, the 1 st negative lens, the 2 nd negative lens, the positive lens, and the 3 rd negative lens are arranged in this order from the object side along the optical axis as the 2 nd lens group, and the positive lens and the 3 rd negative lens are joined.

A method of manufacturing a zoom lens according to the present invention includes disposing a 1 st lens group having positive power, a2 nd lens group having negative power, a 3 rd lens group having positive power, a 4 th lens group having negative power, and a 5 th lens group having positive power in this order from an object side along an optical axis, and moving the 1 st lens group, the 2 nd lens group, the 3 rd lens group, the 4 th lens group, and the 5 th lens group along the optical axis so that a distance between the 1 st lens group and the 2 nd lens group, a distance between the 2 nd lens group and the 3 rd lens group, a distance between the 3 rd lens group and the 4 th lens group, and a distance between the 4 th lens group and the 5 th lens group respectively change when zooming from a wide-angle end state to a telephoto end state, and satisfies the following conditional expressions:

-0.90<f2/TL2<-0.60

-0.180<f4/ft<-0.140

wherein,

f 2: a focal length of the 2 nd lens group,

TL 2: a length on the optical axis of the 2 nd lens group,

f 4: a focal length of the 4 th lens group,

ft: and the focal length of the zoom lens in a far focus end state.

Effects of the invention

According to any one of the present invention, a zoom lens, an optical apparatus, and a zoom lens manufacturing method that are small and have a large magnification ratio and good optical performance can be provided.

Drawings

Fig. 1(a) is a lens configuration diagram in a wide-angle end state, fig. 1(b) is a lens configuration diagram in an intermediate focal length state, and fig. 1(c) is a lens configuration diagram in a telephoto end state of the zoom lens according to embodiment 1.

Fig. 2(a) is each aberration diagram at the time of infinity focusing in the wide-angle end state, fig. 2(b) is each aberration diagram at the time of infinity focusing in the intermediate focal length state, and fig. 2(c) is each aberration diagram at the time of infinity focusing in the far-focus end state of the zoom lens according to embodiment 1.

Fig. 3(a) is a lens structural view in the wide-angle end state, fig. 3(b) is a lens structural view in the intermediate focal length state, and fig. 3(c) is a lens structural view in the telephoto end state of the zoom lens of embodiment 2.

Fig. 4(a) is each aberration diagram at the time of infinity focusing in the wide-angle end state, fig. 4(b) is each aberration diagram at the time of infinity focusing in the intermediate focal length state, and fig. 4(c) is each aberration diagram at the time of infinity focusing in the far-focus end state of the zoom lens according to embodiment 2.

Fig. 5(a) is a lens structural view in the wide-angle end state, fig. 5(b) is a lens structural view in the intermediate focal length state, and fig. 5(c) is a lens structural view in the telephoto end state of the zoom lens of embodiment 3.

Fig. 6(a) is each aberration diagram in infinity focusing in the wide-angle end state, fig. 6(b) is each aberration diagram in infinity focusing in the intermediate focal length state, and fig. 6(c) is each aberration diagram in infinity focusing in the far-focus end state of the zoom lens according to embodiment 3.

Fig. 7(a) is a front view of the digital still camera, and fig. 7(b) is a rear view of the digital still camera.

Fig. 8 is a sectional view taken along an arrow a-a' in fig. 7 (a).

Fig. 9 is a flowchart illustrating a method of manufacturing the zoom lens according to embodiment 1.

Fig. 10 is a flowchart illustrating a method of manufacturing the zoom lens of embodiment 2.

Fig. 11 is a flowchart illustrating a method of manufacturing the zoom lens of embodiment 3.

Detailed Description

Hereinafter, embodiment 1 will be described with reference to the drawings. The digital still camera CAM of embodiment 1 having the zoom lens of embodiment 1 is shown in fig. 7 and 8. In fig. 7, fig. 7(a) shows a front view of the digital still camera CAM, and fig. 7(b) shows a rear view of the digital still camera CAM. Fig. 8 shows a cross-sectional view along the arrow a-a' in fig. 7 (a).

In the digital still camera CAM shown in fig. 7, when a power button (not shown) is pressed, a shutter (not shown) of a photographing lens (ZL) is opened, and light from a subject (object) is condensed by the photographing lens (ZL) and focused on an image pickup device C (for example, a CCD, a CMOS, or the like) disposed on an image plane I shown in fig. 8. The subject image formed on the image pickup device C is displayed on a liquid crystal monitor M disposed behind the digital still camera CAM. After the photographer specifies the composition of the subject image while viewing the liquid crystal monitor M, the release button B1 is pressed to photograph the subject image with the image pickup device, and the subject image is recorded and stored in a memory not shown.

The photographing lens is composed of a zoom lens ZL according to embodiment 1 described later. In addition, in the digital still camera CAM is configured with: an auxiliary light emitting portion DL for emitting auxiliary light when the subject is dark; a wide (W) -telephoto (D) button B2 for zooming (varying magnification) the photographing lens (zoom lens ZL) from the wide-angle end state (W) to the telephoto end state (T); and a function button B3 used for setting various conditions of the digital still camera CAM, and the like.

As shown in fig. 1, the zoom lens ZL of embodiment 1 includes, for example, a 1 st lens group G1 having positive power, a2 nd lens group G2 having negative power, a 3 rd lens group G3 having positive power, a 4 th lens group G4 having negative power, and a 5 th lens group G5 having positive power, which are arranged in this order from the object side along the optical axis. Upon varying magnification (zooming) from the wide-angle end state to the telephoto end state, the 1 st lens group G1, the 2 nd lens group G2, the 3 rd lens group G3, the 4 th lens group G4, and the 5 th lens group G5 move along the optical axis respectively in such a manner that an interval between the 1 st lens group G1 and the 2 nd lens group G2, an interval between the 2 nd lens group G2 and the 3 rd lens group G3, an interval between the 3 rd lens group G3 and the 4 th lens group G4, and an interval between the 4 th lens group G4 and the 5 th lens group G5 respectively vary. The zoom lens ZL satisfies the condition represented by the following conditional expression (1).

0.25<f1/ft<0.38…(1)

Wherein,

f 1: the focal length of the 1 st lens group G1,

ft: a focal length of the zoom lens ZL in a far-focus end state.

The conditional expression (1) is a conditional expression for specifying the focal length of the 1 st lens group G1 with respect to the focal length in the telephoto end state of the entire zoom lens ZL system. By satisfying the conditional expression (1), the telephoto ratio in the telephoto end state can be reduced, and the total length of the zoom lens ZL can be shortened. This makes it possible to realize a zoom lens ZL that is small, has a large zoom ratio, and has good optical performance. If the condition exceeds the upper limit value of the conditional expression (1), the zoom lens ZL becomes large. In the condition exceeding the upper limit value of the conditional expression (1), when downsizing of the zoom lens ZL is realized, the optical power of the 1 st lens group G1 becomes small, so it is necessary to increase the optical power of the 3 rd lens group G3, spherical aberration is seriously generated on the negative side in the entire variable power region, and therefore it is not preferable. On the other hand, if the condition is lower than the lower limit value of the conditional expression (1), the 1 st lens group G1 is not preferable because the power becomes large and spherical aberration and field curvature are generated seriously on the negative side in the telephoto end state.

In order to more reliably obtain the effect of embodiment 1, the upper limit value of conditional expression (1) is preferably set to 0.34. Further, it is more preferable to set the upper limit value of the conditional expression (1) to 0.33. On the other hand, in order to more reliably obtain the effect of embodiment 1, it is preferable to set the lower limit value of conditional expression (1) to 0.30.

In the zoom lens ZL according to embodiment 1, it is preferable that the condition expressed by the following conditional expression (2) is satisfied.

-0.180<(f1×fw)/(f2×ft)<-0.160…(2)

Wherein,

fw: a focal length in the wide-angle end state of the zoom lens ZL,

f 2: focal length of the 2 nd lens group G2.

The conditional expression (2) is a conditional expression that specifies the focal length of the 1 st lens group G1 with respect to the focal length of the 2 nd lens group G2. By satisfying the conditional expression (2), a compact zoom lens ZL having high imaging performance can be realized. When the condition exceeds the upper limit of the conditional expression (2), spherical aberration is generated seriously on the negative side in the telephoto end state, which is not preferable. On the other hand, if the condition is less than the lower limit of the conditional expression (2), spherical aberration is generated seriously on the positive side in the telephoto end state, which is not preferable.

In order to more reliably obtain the effect of embodiment 1, the upper limit value of conditional expression (2) is preferably set to-0.167. On the other hand, in order to more reliably obtain the effect of embodiment 1, it is preferable to set the lower limit value of conditional expression (2) to-0.176.

In the zoom lens ZL of embodiment 1, it is preferable that the 1 st lens group G1 has three positive lenses. With this configuration, spherical aberration and coma can be corrected satisfactorily in the state of the far-focus end.

In the zoom lens ZL of embodiment 1, it is preferable that the 1 st lens group G1 has a cemented lens of a positive lens and a negative lens, and satisfies the conditions represented by the following conditional expression (3) and conditional expression (4).

0.367<nN1-nP1…(3)

80<νP1…(4)

Wherein,

nN 1: the refractive index of the negative lens of the cemented lens constituting the 1 st lens group G1 with respect to the d-line,

nP 1: the refractive index of the positive lens of the cemented lens constituting the 1 st lens group G1 with respect to the d-line,

ν P1: abbe number of the positive lens of the cemented lens constituting the 1 st lens group G1.

The conditional expression (3) is a conditional expression for defining a difference in refractive index between the positive lens and the negative lens of the cemented lens constituting the 1 st lens group G1. By satisfying the conditional expression (3), spherical aberration generated in the 1 st lens group G1 can be corrected well. If the condition is lower than the lower limit value of the conditional expression (3), the refractive index difference between the positive lens and the negative lens of the cemented lens constituting the 1 st lens group G1 becomes too small, and the curvature of spherical aberration becomes too large in the telephoto end state, which is not preferable.

In order to more reliably obtain the effect of embodiment 1, the lower limit value of conditional expression (3) is preferably set to 0.370.

The conditional expression (4) is a conditional expression for defining the abbe number of the positive lens of the cemented lens constituting the 1 st lens group G1. By satisfying the conditional expression (4), it is possible to correct the axial chromatic aberration and the magnification chromatic aberration in the telephoto end state. If the condition is lower than the lower limit of the conditional expression (4), it is not preferable because the axial chromatic aberration is generated seriously on the negative side and the magnification chromatic aberration is generated seriously on the positive side in the telephoto end state.

In order to more reliably obtain the effect of embodiment 1, the lower limit value of conditional expression (4) is preferably set to 90. Further, since the positive lens satisfying the conditional expression (4) is soft and easily damaged, it is preferable to dispose and bond a negative lens on the object side of the positive lens. With this configuration, since the object-side lens surface of the positive lens is covered with the negative lens, the object-side lens surface of the positive lens satisfying the conditional expression (4) is hardly damaged.

In the zoom lens ZL according to embodiment 1, it is preferable that the condition represented by the following conditional expression (5) is satisfied.

-0.18<f4/ft<-0.14…(5)

Wherein,

f 4: focal length of the 4 th lens group 4.

The conditional expression (5) is a conditional expression for specifying the focal length of the 4 th lens group G4 with respect to the focal length in the telephoto end state of the entire zoom lens ZL system. By satisfying the conditional expression (5), the front lens diameter of the zoom lens ZL can be reduced. When the condition exceeds the upper limit of the conditional expression (5), spherical aberration is generated seriously on the positive side in the wide-angle end state, which is not preferable. On the other hand, if the condition is lower than the lower limit value of the conditional expression (5), the effect of the negative lens on the image side of the aperture stop S is small, and it is difficult to sufficiently reduce the front lens diameter of the zoom lens ZL.

In order to more reliably obtain the effect of embodiment 1, the upper limit value of conditional expression (5) is preferably set to-0.15. On the other hand, in order to more reliably obtain the effect of embodiment 1, it is preferable to set the lower limit value of conditional expression (5) to-0.17.

In the zoom lens ZL of embodiment 1, it is preferable that the 4 th lens group G4 be composed of a cemented lens of one positive lens and one negative lens. With this configuration, axial chromatic aberration in the 4 th lens group G4 alone can be corrected satisfactorily, and correction of axial chromatic aberration in the entire zoom lens ZL system becomes easy. In addition, performance deterioration when the 4 th lens group G4 is decentered can be reduced. The 5 th lens group G5 may be a cemented lens of one positive lens and one negative lens, and the same effects as those in the 4 th lens group G4 can be obtained by this configuration.

In the zoom lens ZL according to embodiment 1, it is preferable that the aperture stop S is disposed in the vicinity of the object side of the 3 rd lens group G3 so as to satisfy the condition expressed by the following conditional expression (6).

0.084<ΔZwt/ft<0.090…(6)

Wherein,

Δ Zwt: a moving distance of the aperture stop S to the object side on the optical axis when zooming from the wide-angle end state to the telephoto end state.

The conditional expression (6) is a conditional expression for specifying a moving distance of the aperture stop S to the object side on the optical axis when the magnification is changed from the wide-angle end state to the telephoto end state with respect to the focal length in the telephoto end state of the entire zoom lens ZL system. In general, the larger the moving distance of the aperture stop S on the optical axis, the larger the amount of change in the F value due to the magnification change. Therefore, by satisfying the conditional expression (6), the amount of change in the F value due to the magnification change from the wide-angle end state to the telephoto end state can be set in an appropriate range, and the focal length of the entire system in the telephoto end state can be increased to secure a large magnification ratio. When the condition exceeds the upper limit value of the conditional expression (6), the F value in the telephoto end state becomes larger than necessary, or the F value in the wide-angle end state becomes smaller, and it becomes difficult to correct spherical aberration, which is not preferable. On the other hand, if the condition is lower than the lower limit value of conditional expression (6), if the F value in the wide-angle end state is to be decreased, the F value in the telephoto end state is also decreased, and it is difficult to correct spherical aberration, which is not preferable.

In order to more reliably obtain the effect of embodiment 1, the upper limit value of conditional expression (6) is preferably set to 0.088. On the other hand, in order to more reliably obtain the effect of embodiment 1, it is preferable to set the lower limit value of conditional expression (6) to 0.086.

Here, a method for manufacturing the zoom lens ZL according to embodiment 1 will be described with reference to fig. 9. First, in a cylindrical lens barrel, a 1 ST lens group G1 having positive power, a2 nd lens group G2 having negative power, a 3 rd lens group G3 having positive power, a 4 th lens group G4 having negative power, and a 5 th lens group G5 having positive power are assembled in this order from the object side (step ST 10). The 1 ST lens group G1, the 2 nd lens group G2, the 3 rd lens group G3, the 4 th lens group G4, and the 5 th lens group G5 are drivably constituted so that the 1 ST lens group G1, the 2 nd lens group G2, the 3 rd lens group G3, the 4 th lens group G4, and the 5 th lens group G5 move along the optical axis to perform magnification change (zooming) from the wide-angle end state to the telephoto end state (step ST 20).

In step ST10 of lens assembly, the 1 ST lens group G1, the 2 nd lens group G2, the 3 rd lens group G3, the 4 th lens group G4, and the 5 th lens group G5 are arranged so as to satisfy the above conditional expression (1) and the like. According to the manufacturing method described above, a zoom lens ZL having a small size, a large magnification ratio, and good optical performance can be obtained.

Next, embodiment 2 will be described with reference to the drawings. Fig. 7 and 8 illustrate a digital still camera CAM having a zoom lens ZL according to embodiment 2 described later. Since the configuration of the digital still camera CAM is already described, similarly to the digital still camera CAM according to embodiment 1, the description thereof will be omitted.

As shown in fig. 1, the zoom lens ZL of embodiment 2 has, for example, a 1 st lens group G1 having positive power, a2 nd lens group G2 having negative power, a 3 rd lens group G3 having positive power, a 4 th lens group G4 having negative power, and a 5 th lens group G5 having positive power, which are arranged in this order from the object side along the optical axis. Upon varying magnification (zooming) from the wide-angle end state to the telephoto end state, the 1 st lens group G1, the 2 nd lens group G2, the 3 rd lens group G3, the 4 th lens group G4, and the 5 th lens group G5 move along the optical axis respectively in such a manner that an interval between the 1 st lens group G1 and the 2 nd lens group G2, an interval between the 2 nd lens group G2 and the 3 rd lens group G3, an interval between the 3 rd lens group G3 and the 4 th lens group G4, and an interval between the 4 th lens group G4 and the 5 th lens group G5 respectively vary.

The 2 nd lens group G2 is composed of a 1 st negative lens, a2 nd negative lens, a positive lens, and a 3 rd negative lens arranged in this order from the object side along the optical axis, and the positive lens and the 3 rd negative lens are joined. With this configuration, it is possible to favorably correct chromatic aberration of magnification in the wide-angle end state and reduce variation in chromatic aberration when zooming from the wide-angle end state to the telephoto end state. This makes it possible to realize a zoom lens ZL that is small, has a large magnification ratio, and has good optical performance.

In the zoom lens ZL according to embodiment 2, it is preferable that the condition represented by the following conditional expression (7) is satisfied.

-0.180<(f1×fw)/(f2×ft)<-0.160…(7)

Wherein,

fw: a focal length in the wide-angle end state of the zoom lens ZL,

ft: a focal length of the zoom lens ZL in a state of a far focus end,

f 1: the focal length of the 1 st lens group G1,

f 2: focal length of the 2 nd lens group G2.

The conditional expression (7) is a conditional expression that specifies the focal length of the 1 st lens group G1 with respect to the focal length of the 2 nd lens group G2. By satisfying the conditional expression (7), a compact zoom lens ZL having high imaging performance can be realized. When the condition exceeds the upper limit of the conditional expression (7), spherical aberration is generated seriously on the negative side in the telephoto end state, which is not preferable. On the other hand, if the condition is lower than the lower limit value of conditional expression (7), spherical aberration is generated seriously on the positive side in the telephoto end state, which is not preferable.

In order to more reliably obtain the effect of embodiment 2, the upper limit value of conditional expression (7) is preferably set to-0.167. On the other hand, in order to more reliably obtain the effect of embodiment 2, it is preferable to set the lower limit value of conditional expression (7) to-0.176.

In the zoom lens ZL according to embodiment 2, it is preferable that the condition represented by the following conditional expression (8) is satisfied.

-0.180<f4/ft<-0.140…(8)

Wherein,

ft: a focal length of the zoom lens ZL in a state of a far focus end,

f 4: focal length of the 4 th lens group G4.

The conditional expression (8) is a conditional expression for specifying the focal length of the 4 th lens group G4 with respect to the focal length in the telephoto end state of the entire zoom lens ZL system. By satisfying the conditional expression (8), the front lens diameter of the zoom lens ZL can be reduced. When the condition exceeds the upper limit of the conditional expression (8), spherical aberration is generated seriously on the positive side in the wide-angle end state, which is not preferable. On the other hand, if the condition is lower than the lower limit value of the conditional expression (8), the effect of the negative lens on the image side of the aperture stop S becomes small, and it is difficult to sufficiently reduce the front lens diameter of the zoom lens ZL.

In order to more reliably obtain the effect of embodiment 2, the upper limit value of conditional expression (8) is preferably set to-0.150. On the other hand, in order to more reliably obtain the effect of embodiment 2, it is preferable to set the lower limit value of conditional expression (8) to-0.170.

In the zoom lens ZL of embodiment 2, the 4 th lens group G4 is preferably composed of a cemented lens of one positive lens and one negative lens. With this configuration, axial chromatic aberration in the 4 th lens group G4 alone can be corrected satisfactorily, and correction of axial chromatic aberration in the entire system of the zoom lens ZL becomes easy. In addition, performance deterioration when the 4 th lens group G4 is decentered can be reduced. The 5 th lens group G5 may be a cemented lens of one positive lens and one negative lens, and the same effects as those in the 4 th lens group G4 can be obtained by this configuration.

Here, a method for manufacturing the zoom lens ZL according to embodiment 2 will be described with reference to fig. 10. First, in a cylindrical lens barrel, a 1 ST lens group G1 having positive power, a2 nd lens group G2 having negative power, a 3 rd lens group G3 having positive power, a 4 th lens group G4 having negative power, and a 5 th lens group G5 having positive power are assembled in this order from the object side (step ST 10). The 1 ST lens group G1, the 2 nd lens group G2, the 3 rd lens group G3, the 4 th lens group G4, and the 5 th lens group G5 are drivably constituted so that the 1 ST lens group G1, the 2 nd lens group G2, the 3 rd lens group G3, the 4 th lens group G4, and the 5 th lens group G5 move along the optical axis to perform magnification change (zooming) from the wide-angle end state to the telephoto end state (step ST 20).

In step ST10 of lens assembly, a 1 ST negative lens, a2 nd negative lens, a positive lens, and a 3 rd negative lens are disposed in this order from the object side along the optical axis as a2 nd lens group G2, and the positive lens and the 3 rd negative lens are joined. By this manufacturing method, a zoom lens ZL which is small in size, has a large magnification ratio, and has good optical performance can be obtained.

Next, embodiment 3 will be described with reference to the drawings. Fig. 7 and 8 illustrate a digital still camera CAM having a zoom lens ZL according to embodiment 3 described later. Since the configuration of the digital still camera CAM is already described, similarly to the digital still camera CAM according to embodiment 1, the description thereof will be omitted.

As shown in fig. 1, the zoom lens ZL of embodiment 3 includes, for example, a 1 st lens group G1 having positive power, a2 nd lens group G2 having negative power, a 3 rd lens group G3 having positive power, a 4 th lens group G4 having negative power, and a 5 th lens group G5 having positive power, which are arranged in this order from the object side along the optical axis. Upon varying magnification (zooming) from the wide-angle end state to the telephoto end state, the 1 st lens group G1, the 2 nd lens group G2, the 3 rd lens group G3, the 4 th lens group G4, and the 5 th lens group G5 move along the optical axis respectively in such a manner that an interval between the 1 st lens group G1 and the 2 nd lens group G2, an interval between the 2 nd lens group G2 and the 3 rd lens group G3, an interval between the 3 rd lens group G3 and the 4 th lens group G4, and an interval between the 4 th lens group G4 and the 5 th lens group G5 respectively vary. The zoom lens ZL satisfies the conditions expressed by the following conditional expressions (9) to (10).

-0.90<f2/TL2<-0.60…(9)

-0.180<f4/ft<-0.140…(10)

Wherein,

f 2: the focal length of the 2 nd lens group G2,

TL 2: the length on the optical axis of the 2 nd lens group G2,

f 4: the focal length of the 4 th lens group G4,

ft: a focal length of the zoom lens ZL in a far-focus end state.

By satisfying the conditional expressions (9) to (10), a zoom lens ZL having a small size, a large magnification ratio, and good optical performance can be realized.

The conditional expression (9) is a conditional expression for defining the focal length of the 2 nd lens group G2 with respect to the length on the optical axis of the 2 nd lens group G2. By satisfying the conditional expression (9), the length of the 2 nd lens group G2 on the optical axis is shortened, and the moving amount at the time of magnification change of the 2 nd lens group G2 can be secured without lengthening the total length of the zoom lens ZL. Further, when the condition is lower than the lower limit value of the conditional expression (9), the length of the 2 nd lens group G2 on the optical axis is undesirably long, the total optical length is undesirably long, or the principal point distance of the 2 nd lens group G2 is undesirably short, and spherical aberration is generated seriously on the positive side in the telephoto end state. On the other hand, if the condition exceeds the upper limit value of the conditional expression (9), the focal length of the 2 nd lens group G2 becomes long, and the moving amount of the 2 nd lens group G2 becomes large to secure the zoom ratio, which leads to an increase in the size of the zoom lens ZL. When downsizing of the zoom lens ZL is realized under the condition exceeding the upper limit value of the conditional expression (9), it is necessary to increase the powers of the 3 rd lens group G3 and the 4 th lens group G4 and to decrease the telephoto ratio in the 3 rd lens group G3 and the 4 th lens group G4, spherical aberration is seriously generated on the negative side in the entire region of the variable power region, and thus it is not preferable.

In order to more reliably obtain the effect of embodiment 3, it is preferable to set the upper limit value of conditional expression (9) to-0.69. Further, it is more preferable that the upper limit value of the conditional expression (9) is set to-0.72. On the other hand, in order to more reliably obtain the effect of embodiment 3, it is preferable to set the lower limit value of conditional expression (9) to-0.81. Further, it is more preferable that the lower limit of conditional expression (9) is set to-0.77.

The conditional expression (10) is a conditional expression for specifying the focal length of the 4 th lens group G4 with respect to the focal length in the telephoto end state of the entire zoom lens ZL system. By satisfying the conditional expression (10), the front lens diameter of the zoom lens ZL can be reduced. Further, when the condition exceeds the upper limit of the conditional expression (10), spherical aberration is generated seriously on the positive side in the wide-angle end state, which is not preferable. On the other hand, if the condition is less than the lower limit of the conditional expression (10), the effect of the negative lens on the image side of the aperture stop S becomes small, and it is difficult to sufficiently reduce the front lens diameter of the zoom lens ZL.

In order to more reliably obtain the effect of embodiment 3, it is preferable to set the upper limit value of conditional expression (10) to-0.150. On the other hand, in order to more reliably obtain the effect of embodiment 3, it is preferable to set the lower limit value of conditional expression (10) to-0.170.

In the zoom lens ZL according to embodiment 3, it is preferable that the condition represented by the following conditional expression (11) is satisfied.

-0.180<(f1×fw)/(f2×ft)<-0.160…(11)

Wherein,

f 1: the focal length of the 1 st lens group G1,

fw: a focal length in the wide-angle end state of the zoom lens ZL.

The conditional expression (11) is a conditional expression that specifies the focal length of the 1 st lens group G1 with respect to the focal length of the 2 nd lens group G2. By satisfying the conditional expression (3), a compact zoom lens ZL having high imaging performance can be realized. When the condition exceeds the upper limit of the conditional expression (11), spherical aberration is generated seriously on the negative side in the telephoto end state, which is not preferable. On the other hand, if the condition is less than the lower limit of the conditional expression (11), spherical aberration is generated seriously on the positive side in the telephoto end state, which is not preferable.

In order to more reliably obtain the effect of embodiment 3, it is preferable to set the upper limit value of conditional expression (11) to-0.167. On the other hand, in order to more reliably obtain the effect of embodiment 3, it is preferable to set the lower limit value of conditional expression (11) to-0.176.

In the zoom lens ZL of embodiment 3, the 4 th lens group G4 is preferably composed of a cemented lens of one positive lens and one negative lens. With this configuration, axial chromatic aberration in the 4 th lens group G4 alone can be corrected satisfactorily, and correction of axial chromatic aberration in the entire system of the zoom lens ZL becomes easy. In addition, performance deterioration when the 4 th lens group G4 is decentered can be reduced. The 5 th lens group G5 may be a cemented lens of one positive lens and one negative lens, and the same effects as those in the 4 th lens group G4 can be obtained by this configuration.

In the zoom lens ZL according to embodiment 3, it is preferable that the condition represented by the following conditional expression (12) is satisfied.

0.20<(n2f×ft)/(ν2f×r2f)<1.00…(12)

Wherein,

n2 f: the refractive index to d-line of the most image side lens in the 2 nd lens group G2,

ft: a focal length of the zoom lens ZL in a state of a far focus end,

v 2 f: abbe number of the most image side lens in the 2 nd lens group G2,

r2 f: radius of curvature of the most image side lens surface in the 2 nd lens group G2.

The conditional expression (12) is a conditional expression for specifying the refractive index of the most image side lens in the 2 nd lens group G2 with respect to the d-line and the radius of curvature of the most image side lens surface in the 2 nd lens group G2. By satisfying the conditional expression (12), the total length of the zoom lens ZL in the telephoto end state can be shortened while maintaining good optical performance. When the condition exceeds the upper limit value of the conditional expression (12), the radius of curvature of the most image-side lens surface in the 2 nd lens group G2 is small. In this case, it is necessary to increase the distance between the 2 nd lens group G2 and the aperture stop S in the telephoto end state, and the total length of the zoom lens ZL in the telephoto end state becomes longer, which is not preferable. On the other hand, if the condition is lower than the lower limit of conditional expression (12), the field curvature is not preferable because it is severely generated on the positive side in the wide-angle end state.

In order to more reliably obtain the effect of embodiment 3, the upper limit value of conditional expression (12) is preferably set to 0.73. Further, it is more preferable to set the upper limit value of conditional expression (12) to 0.50. On the other hand, in order to more reliably obtain the effect of embodiment 3, it is preferable to set the lower limit value of conditional expression (12) to 0.29. Further, it is more preferable to set the lower limit of conditional expression (12) to 0.35.

Here, a method for manufacturing the zoom lens ZL according to embodiment 3 will be described with reference to fig. 11. First, in a cylindrical lens barrel, a 1 ST lens group G1 having positive power, a2 nd lens group G2 having negative power, a 3 rd lens group G3 having positive power, a 4 th lens group G4 having negative power, and a 5 th lens group G5 having positive power are assembled in this order from the object side (step ST 10). The 1 ST lens group G1, the 2 nd lens group G2, the 3 rd lens group G3, the 4 th lens group G4, and the 5 th lens group G5 are drivably constituted so that the 1 ST lens group G1, the 2 nd lens group G2, the 3 rd lens group G3, the 4 th lens group G4, and the 5 th lens group G5 move along the optical axis to perform magnification change (zooming) from the wide-angle end state to the telephoto end state (step ST 20).

In step ST10 of lens assembly, the 1 ST lens group G1, the 2 nd lens group G2, the 3 rd lens group G3, the 4 th lens group G4, and the 5 th lens group G5 are arranged so as to satisfy the above-described conditional expressions (9) to (10) and the like. By this manufacturing method, a zoom lens ZL which is small in size, has a large magnification ratio, and has good optical performance can be obtained.

Examples of embodiments 1 to 3

(embodiment 1)

Hereinafter, embodiments of the present application will be described with reference to the drawings. First, embodiment 1 of the present application will be described with reference to fig. 1 to 2 and table 1. Fig. 1(a) is a lens configuration diagram in a wide-angle end state, fig. 1(b) is a lens configuration diagram in an intermediate focal length state, and fig. 1(c) is a lens configuration diagram in a far-focus end state of a zoom lens ZL (ZL1) of embodiment 1. The zoom lens ZL1 of embodiment 1 has, in order from the object side along the optical axis, a 1 st lens group G1 having positive power, a2 nd lens group G2 having negative power, a 3 rd lens group G3 having positive power, a 4 th lens group G4 having negative power, and a 5 th lens group G5 having positive power. Further, upon magnification (zooming) from the wide-angle end state to the telephoto end state, the 1 st lens group G1, the 2 nd lens group G2, the 3 rd lens group G3, the 4 th lens group G4, and the 5 th lens group G5 move along the optical axis respectively in such a manner that an interval between the 1 st lens group G1 and the 2 nd lens group G2 increases, an interval between the 2 nd lens group G2 and the 3 rd lens group G3 decreases, an interval between the 3 rd lens group G3 and the 4 th lens group G4 varies, and an interval between the 4 th lens group G4 and the 5 th lens group G5 varies.

The 1 st lens group G1 includes, in order from the object side along the optical axis, a meniscus-shaped negative lens L11 with the convex surface facing the object side, a biconvex 1 st positive lens L12, a meniscus-shaped 2 nd positive lens L13 with the convex surface facing the object side, and a meniscus-shaped 3 rd positive lens L14 with the convex surface facing the object side. In the 1 st lens group G1, the negative lens L11 and the 1 st positive lens L12 become cemented lenses cemented with each other.

The 2 nd lens group G2 includes a 1 st negative lens L21, a biconcave 2 nd negative lens L22, a biconvex positive lens L23, and a biconcave 3 rd negative lens L24, which are arranged in this order from the object side along the optical axis and have convex surfaces facing the image plane I. In the 2 nd lens group G2, the positive lens L23 and the 3 rd negative lens L24 become cemented lenses cemented with each other.

The 3 rd lens group G3 is composed of a biconvex 1 st positive lens L31, a biconvex 2 nd positive lens L32, a biconcave negative lens L33, and a biconvex 3 rd positive lens L34, which are arranged in this order from the object side along the optical axis. In the 3 rd lens group G3, the 2 nd positive lens L32 and the negative lens L33 become cemented lenses cemented with each other. Further, both lens surfaces of the 1 st positive lens L31 are aspheric.

The 4 th lens group G4 is composed of a biconvex positive lens L41 and a biconcave negative lens L42 arranged in order from the object side along the optical axis. In the 4 th lens group G4, the positive lens L41 and the negative lens L42 become cemented lenses cemented with each other.

The 5 th lens group G5 is composed of a biconvex positive lens L51 and a meniscus negative lens L52 whose convex surface faces the image plane I side, which are arranged in order from the object side along the optical axis. In the 5 th lens group G5, the positive lens L51 and the negative lens L52 become cemented lenses cemented with each other. The object-side lens surface of the positive lens L51 is aspheric.

The aperture stop S is disposed in the vicinity of the object side of the 3 rd lens group G3, and moves on the same trajectory as that of the 3 rd lens group G3 when zooming (zooming) from the wide-angle end state to the telephoto end state. Focusing from an infinity object to a close object (finite distance object) is performed by moving the 5 th lens group G5 to the object side along the optical axis. The filter group FL arranged between the 5 th lens group G5 and the image plane I is composed of a low-pass filter, an infrared filter, and the like.

Tables 1 to 3, which are tables showing values of parameters of the zoom lenses according to embodiments 1 to 3, respectively, are shown below. The [ overall parameters ] in each table show values of the focal length F, F value FNO, half field angle ω, and image height Y of the zoom lens ZL in each of the wide-angle end state, intermediate focal length state, and telephoto end state. In [ lens parameters ], the 1 st column (surface number) indicates the number of the lens surface from the object side, the 2 nd column R indicates the radius of curvature of the lens surface, the 3 rd column D indicates the interval on the optical axis of the lens surface, the 4 th column vd indicates the abbe number for the D-line (wavelength λ is 587.6nm), and the 5 th column nd indicates the refractive index for the D-line (wavelength λ is 587.6 nm). In addition, the right-hand symbol in column 1 (surface number) indicates that the lens surface is an aspherical surface. The curvature radius "0.0000" indicates a plane, and the refractive index nd of air is 1.000000, and the description thereof is omitted.

About [ aspherical surface data ]]The aspherical surface coefficients shown in (a) are expressed by the following expression (a) where y represents the height in the direction perpendicular to the optical axis, x (y) represents the distance (amount of recess) along the optical axis from the tangent plane at the vertex of each aspherical surface to each aspherical surface at the height y, R represents the paraxial radius of curvature (radius of curvature of the reference spherical surface), κ represents the conic constant, and An represents the aspherical surface coefficients n times (n is 4, 6, 8, and 10). In each example, the 2-th aspheric surface coefficient a2 is 0, and the description thereof is omitted. In addition, in [ aspherical data ]]Wherein "E-n" represents ". times.10^-n”。

X(y)＝(y²/R)/{1+(1-κ×y²/R²)^1/2}+A4×y⁴+A6×y⁶+A8×y⁸+A10×y¹⁰

…(A)

The values of the focal length f, the variable interval, the back focal length BF, and the total length TL (the length from the first optical surface to the final optical surface (image plane I) of the zoom lens ZL) in each of the wide-angle end state, the intermediate focal length state, and the far-focus end state (at the time of infinity focusing) are shown in [ variable interval data ]. The values of the focal lengths of the respective lens groups are shown in [ lens group focal lengths ], respectively. The corresponding value of each conditional expression is shown in [ conditional expression corresponding value ].

In addition, the unit of the focal length f, the radius of curvature R, and other lengths described in all the following parameter values is generally "mm", but the same optical performance can be obtained even if the optical system is scaled up or down, and therefore, the present invention is not limited thereto. The same reference numerals as in the present embodiment are used for parameter values in embodiments 2 to 3 described later.

Table 1 below shows parameters in example 1. The radii of curvature R of the 1 st to 28 th surfaces in table 1 correspond to the reference numerals R1 to R28 indicated by the 1 st to 28 th surfaces in fig. 1 (a). The 29 th to 32 nd surfaces are flat surfaces, and corresponding surfaces are not shown in fig. 1 (a). Group numbers G1 to G5 in table 1 correspond to the respective lens groups G1 to G5 in fig. 1. In embodiment 1, each lens surface of the 16 th, 17 th and 26 th surfaces is formed in an aspherical shape.

(Table 1)

[ Overall parameters ]

Zoom ratio of 56.905

[ lens parameters ]

[ aspherical data ]

The 16 th surface

κ＝-0.3575,A4＝1.79600E-04,A6＝4.41968E-07,A8＝0.00000E+00,A10＝0.00000E+00

The 17 th surface

κ＝1.0000,A4＝4.43002E-05,A6＝-4.79298E-08,A8＝0.00000E+00,A10＝0.00000E+00

The 26 th surface

κ＝1.0000,A4＝2.13923E-05,A6＝1.24506E-07,A8＝0.00000E+00,A10＝0.00000E+00

[ variable Interval data ]

[ focal length of lens group ]

[ corresponding values of conditional expressions ]

Conditional expression (1) f1/ft 0.32

Conditional expressions (2), (7), (11) (f1 × fw)/(f2 × ft) — 0.167

Conditional expression (3) nN1-nP1 ═ 0.367

Conditional expression (4) ν P1 ═ 95.00

Conditional expressions (5), (8), (10) f 4/ft-0.148

Conditional expression (6) Δ Zwt/ft ═ 0.089

Conditional expression (9) f2/TL2 ═ 0.810

Conditional expression (12) (n2f × ft)/(ν 2f × r2f) ═ 0.407

As described above, it is understood that the present example satisfies all of the conditional expressions (1) to (12).

Fig. 2(a) to (c) are aberration diagrams of zoom lens ZL1 according to embodiment 1. Here, fig. 2(a) is each aberration diagram in infinity focusing in the wide-angle end state (f is 4.40mm), fig. 2(b) is each aberration diagram in infinity focusing in the intermediate focal length state (f is 33.00mm), and fig. 2(c) is each aberration diagram in infinity focusing in the far-focus end state (f is 250.30 mm). In each aberration diagram, FNO represents an F value, and Y represents an image height. In each aberration diagram, d represents an aberration on the d-line (λ 587.6nm), and g represents an aberration on the g-line (λ 435.8 nm). In the aberration diagram indicating astigmatism, the solid line indicates a sagittal image surface, and the broken line indicates a meridional image surface. The above description of the aberration diagrams is also the same in the other embodiments.

Further, it is understood that, in embodiment 1, each aberration is corrected well in each focal length state from the wide-angle end state to the telephoto end state by each aberration map, and excellent optical performance is obtained. As a result, by mounting the zoom lens ZL1 of embodiment 1, excellent optical performance can be ensured even in the digital still camera CAM.

(embodiment 2)

Hereinafter, example 2 of the present application will be described with reference to fig. 3 to 4 and table 2. Fig. 3(a) is a lens structural view in the wide-angle end state, fig. 3(b) is a lens structural view in the intermediate focal length state, and fig. 3(c) is a lens structural view in the far-focus end state of the zoom lens ZL (ZL2) of embodiment 2. The zoom lens ZL2 of embodiment 2 has, in order from the object side along the optical axis, a 1 st lens group G1 having positive power, a2 nd lens group G2 having negative power, a 3 rd lens group G3 having positive power, a 4 th lens group G4 having negative power, and a 5 th lens group G5 having positive power. Further, upon magnification (zooming) from the wide-angle end state to the telephoto end state, the 1 st lens group G1, the 2 nd lens group G2, the 3 rd lens group G3, the 4 th lens group G4, and the 5 th lens group G5 move along the optical axis respectively in such a manner that an interval between the 1 st lens group G1 and the 2 nd lens group G2 increases, an interval between the 2 nd lens group G2 and the 3 rd lens group G3 decreases, an interval between the 3 rd lens group G3 and the 4 th lens group G4 varies, and an interval between the 4 th lens group G4 and the 5 th lens group G5 varies.

The 1 st lens group G1 includes, in order from the object side along the optical axis, a meniscus-shaped negative lens L11 with the convex surface facing the object side, a biconvex 1 st positive lens L12, a meniscus-shaped 2 nd positive lens L13 with the convex surface facing the object side, and a meniscus-shaped 3 rd positive lens L14 with the convex surface facing the object side. In the 1 st lens group G1, the negative lens L11 and the 1 st positive lens L12 become cemented lenses cemented with each other.

The 2 nd lens group G2 includes a 1 st negative lens L21, a biconcave 2 nd negative lens L22, a biconvex positive lens L23, and a biconcave 3 rd negative lens L24, which are arranged in this order from the object side along the optical axis and have convex surfaces facing the image plane I. In the 2 nd lens group G2, the positive lens L23 and the 3 rd negative lens L24 become cemented lenses cemented with each other.

The 3 rd lens group G3 is composed of a biconvex 1 st positive lens L31, a2 nd positive lens L32 with a convex surface facing the object side, a negative lens L33 with a concave surface facing the image plane I side, and a biconvex 3 rd positive lens L34, which are arranged in this order from the object side along the optical axis. In the 3 rd lens group G3, the 2 nd positive lens L32 and the negative lens L33 become cemented lenses cemented with each other. Further, both lens surfaces of the 1 st positive lens L31 are aspheric.

The 4 th lens group G4 is composed of a biconvex positive lens L41 and a biconcave negative lens L42 arranged in order from the object side along the optical axis. In the 4 th lens group G4, the positive lens L41 and the negative lens L42 become cemented lenses cemented with each other.

The 5 th lens group G5 is composed of a biconvex positive lens L51 and a meniscus negative lens L52 whose convex surface faces the image plane I side, which are arranged in order from the object side along the optical axis. In the 5 th lens group G5, the positive lens L51 and the negative lens L52 become cemented lenses cemented with each other. The object-side lens surface of the positive lens L51 is aspheric.

The aperture stop S is disposed in the vicinity of the object side of the 3 rd lens group G3, and moves on the same trajectory as that of the 3 rd lens group G3 when zooming (zooming) from the wide-angle end state to the telephoto end state. Focusing from an infinity object to a close object (finite distance object) is performed by moving the 5 th lens group G5 to the object side along the optical axis. The filter group FL arranged between the 5 th lens group G5 and the image plane I is composed of a low-pass filter, an infrared filter, and the like.

The parameters in the 2 nd embodiment are shown in table 2 below. The radii of curvature R of the 1 st to 28 th surfaces in table 2 correspond to the reference numerals R1 to R28 denoted by the 1 st to 28 th surfaces in fig. 3 (a). The 29 th to 32 nd surfaces are flat surfaces, and corresponding surfaces are not shown in fig. 3 (a). Group numbers G1 to G5 in table 2 correspond to the respective lens groups G1 to G5 in fig. 3. In example 2, each lens surface of the 16 th, 17 th and 26 th surfaces is formed in an aspherical shape.

(Table 2)

[ Overall parameters ]

Zoom ratio of 56.96

[ lens parameters ]

[ aspherical data ]

The 16 th surface

κ＝0.5602,A4＝-1.97251E-05,A6＝4.63015E-07,A8＝0.00000E+00,A10＝0.00000E+00

The 17 th surface

κ＝1.0000,A4＝5.07627E-05,A6＝2.26946E-07,A8＝0.00000E+00,A10＝0.00000E+00

The 26 th surface

κ＝1.0000,A4＝2.10907E-05,A6＝1.90396E-07,A8＝0.00000E+00,A10＝0.00000E+00

[ variable Interval data ]

[ focal length of lens group ]

[ corresponding values of conditional expressions ]

Conditional expression (1) f1/ft 0.32

Conditional expressions (2), (7), (11) (f1 × fw)/(f2 × ft) — 0.173

Conditional expression (3) nN1-nP1 ═ 0.367

Conditional expression (4) ν P1 ═ 95.00

Conditional expressions (5), (8), (10) f 4/ft-0.142

Conditional expression (6) Δ Zwt/ft ═ 0.088

Conditional expression (9) f2/TL2 ═ 0.767

Conditional expression (12) (n2f × ft)/(ν 2f × r2f) ═ 0.294

As described above, it is understood that the present example satisfies all of the conditional expressions (1) to (12).

Fig. 4(a) to (c) are aberration diagrams of zoom lens ZL2 of embodiment 2. Here, fig. 4(a) is each aberration diagram in infinity focusing in the wide-angle end state (f is 4.40mm), fig. 4(b) is each aberration diagram in infinity focusing in the intermediate focal length state (f is 33.20mm), and fig. 4(c) is each aberration diagram in infinity focusing in the far-focus end state (f is 250.61 mm). Further, it is found that, in embodiment 2, each aberration is corrected well in each focal length state from the wide-angle end state to the telephoto end state by each aberration map, and excellent optical performance is obtained. As a result, by mounting the zoom lens ZL2 of embodiment 2, excellent optical performance can be ensured even in the digital still camera CAM.

(embodiment 3)

Hereinafter, example 3 of the present application will be described with reference to fig. 5 to 6 and table 3. Fig. 5(a) is a lens structural view in the wide-angle end state, fig. 5(b) is a lens structural view in the intermediate focal length state, and fig. 5(c) is a lens structural view in the far-focus end state of the zoom lens ZL (ZL3) of embodiment 3. The zoom lens ZL3 of embodiment 3 has, in order from the object side along the optical axis, a 1 st lens group G1 having positive power, a2 nd lens group G2 having negative power, a 3 rd lens group G3 having positive power, a 4 th lens group G4 having negative power, and a 5 th lens group G5 having positive power. Further, upon magnification (zooming) from the wide-angle end state to the telephoto end state, the 1 st lens group G1, the 2 nd lens group G2, the 3 rd lens group G3, the 4 th lens group G4, and the 5 th lens group G5 move along the optical axis respectively in such a manner that an interval between the 1 st lens group G1 and the 2 nd lens group G2 increases, an interval between the 2 nd lens group G2 and the 3 rd lens group G3 decreases, an interval between the 3 rd lens group G3 and the 4 th lens group G4 varies, and an interval between the 4 th lens group G4 and the 5 th lens group G5 varies.

The 1 st lens group G1 includes, in order from the object side along the optical axis, a meniscus-shaped negative lens L11 with the convex surface facing the object side, a biconvex 1 st positive lens L12, a meniscus-shaped 2 nd positive lens L13 with the convex surface facing the object side, and a meniscus-shaped 3 rd positive lens L14 with the convex surface facing the object side. In the 1 st lens group G1, the negative lens L11 and the 1 st positive lens L12 become cemented lenses cemented with each other.

The 2 nd lens group G2 includes a 1 st negative lens L21 having a concave surface facing the image plane I side, a2 nd negative lens L22 having a meniscus shape with a convex surface facing the image plane I side, a biconvex positive lens L23, and a biconcave negative lens L24, which are arranged in this order from the object side along the optical axis. In the 2 nd lens group G2, the positive lens L23 and the 3 rd negative lens L24 become cemented lenses cemented with each other.

The 3 rd lens group G3 is composed of a biconvex 1 st positive lens L31, a biconvex 2 nd positive lens L32, a biconcave negative lens L33, and a biconvex 3 rd positive lens L34, which are arranged in this order from the object side along the optical axis. In the 3 rd lens group G3, the 2 nd positive lens L32 and the negative lens L33 become cemented lenses cemented with each other. Further, both lens surfaces of the 1 st positive lens L31 are aspheric.

The 4 th lens group G4 is composed of a meniscus-shaped positive lens L41 having a convex surface facing the object side and a meniscus-shaped negative lens L42 having a convex surface facing the object side, which are arranged in this order from the object side along the optical axis. In the 4 th lens group G4, the positive lens L41 and the negative lens L42 become cemented lenses cemented with each other.

The 5 th lens group G5 is composed of a biconvex positive lens L51 and a meniscus negative lens L52 whose convex surface faces the image plane I side, which are arranged in order from the object side along the optical axis. In the 5 th lens group G5, the positive lens L51 and the negative lens L52 become cemented lenses cemented with each other. The object-side lens surface of the positive lens L51 is aspheric.

The aperture stop S is disposed in the vicinity of the object side of the 3 rd lens group G3, and moves on the same trajectory as that of the 3 rd lens group G3 when zooming (zooming) from the wide-angle end state to the telephoto end state. Focusing from an infinity object to a close object (finite distance object) is performed by moving the 5 th lens group G5 to the object side along the optical axis. The filter group FL arranged between the 5 th lens group G5 and the image plane I is composed of a low-pass filter, an infrared filter, and the like.

The parameters in the 3 rd embodiment are shown in table 3 below. The radii of curvature R of the 1 st to 28 th surfaces in table 3 correspond to the reference numerals R1 to R28 indicated by the 1 st to 28 th surfaces in fig. 5 (a). The 29 th to 32 nd surfaces are flat surfaces, and corresponding surfaces are not shown in fig. 5 (a). Group numbers G1 to G5 in table 3 correspond to the respective lens groups G1 to G5 in fig. 5. In example 3, each lens surface of the 16 th, 17 th and 26 th surfaces is formed in an aspherical shape.

(Table 3)

[ Overall parameters ]

Zoom ratio of 56.835

[ lens parameters ]

[ aspherical data ]

The 16 th surface

κ＝0.5886,A4＝-8.28313E-06,A6＝4.41968E-07,A8＝0.00000E+00,A10＝0.00000E+00

The 17 th surface

κ＝1.0000,A4＝7.83065E-05,A6＝-4.79298E-08,A8＝0.00000E+00,A10＝0.00000E+00

The 26 th surface

κ＝1.0000,A4＝2.13923E-05,A6＝1.24506E-07,A8＝0.00000E+00,A10＝0.00000E+00

[ variable Interval data ]

[ focal length of lens group ]

[ corresponding values of conditional expressions ]

Conditional expression (1) f1/ft 0.30

Conditional expressions (2), (7), (11) (f1 × fw)/(f2 × ft) — 0.176

Conditional expression (3) nN1-nP1 ═ 0.446

Conditional expression (4) ν P1 ═ 95.00

Conditional expressions (5), (8), (10) f 4/ft-0.184

Conditional expression (6) Δ Zwt/ft ═ 0.086

Conditional expression (9) f2/TL2 ═ 0.724

Conditional expression (12) (n2f × ft)/(ν 2f × r2f) is 0.728

As described above, it is understood that the present example satisfies all of the conditional expressions (1) to (12).

Fig. 6(a) to (c) are aberration diagrams of zoom lens ZL3 of embodiment 3. Here, fig. 6(a) is each aberration diagram in infinity focusing in the wide-angle end state (f is 4.40mm), fig. 6(b) is each aberration diagram in infinity focusing in the intermediate focal length state (f is 33.00mm), and fig. 6(c) is each aberration diagram in infinity focusing in the far-focus end state (f is 250.00 mm). Further, it is found that, in embodiment 3, each aberration is corrected well in each focal length state from the wide-angle end state to the telephoto end state by each aberration map, and excellent optical performance is obtained. As a result, by mounting the zoom lens ZL3 according to embodiment 3, excellent optical performance can be ensured even in the digital still camera CAM.

As described above, according to the embodiments, a zoom lens and an optical apparatus (digital still camera) which are small and have a large magnification ratio and have good optical performance can be realized.

In the above-described embodiments, the following can be appropriately employed within a range in which optical performance is not impaired.

In the above-described embodiments, the 5-group configuration is shown as the zoom lens, but the present invention can be applied to other group configurations such as 6 groups. Further, a lens or a lens group may be added to the most object side, or a lens group may be added to the most image side. In addition, the lens group means a portion having at least one lens separated by a varying air interval at the time of magnification variation.

In addition, a single or a plurality of lens groups or a partial lens group may be used as a focusing lens group that moves in the optical axis direction to focus from an infinity object to a close object. The focusing lens group can be applied to autofocus as well as motor drive for autofocus (using an ultrasonic motor or the like). In particular, it is preferable that the 5 th lens group is a focusing lens group.

Further, the lens group or a part of the lens group may be an anti-shake lens group that corrects image shake caused by hand shake by moving the lens group or the part of the lens group so as to have a component in a direction perpendicular to the optical axis or rotationally moving (wobbling) upward in an in-plane direction including the optical axis. In particular, the 3 rd lens group is preferably an anti-shake lens group.

The lens surface may be formed of a spherical surface, a flat surface, or an aspherical surface. When the lens surface is a spherical surface or a flat surface, lens processing and assembly adjustment become easy, and deterioration of optical performance due to errors in processing and assembly adjustment is prevented, which is preferable. Further, even in the case of image plane shift, deterioration in writing performance is small, and therefore, this is preferable. When the lens surface is an aspherical surface, the aspherical surface may be any one of an aspherical surface formed by grinding, a glass molding aspherical surface in which glass is formed into an aspherical shape by a mold, and a composite aspherical surface in which a resin is formed into an aspherical shape on a surface of glass. The lens surface may be a diffraction surface, or the lens may be a refractive index distribution lens (GRIN lens) or a plastic lens.

Further, the aperture stop is preferably disposed in the 3 rd lens group, but a member as the aperture stop may not be provided, and the function thereof may be replaced by a frame of the lens. In addition, in each of the embodiments described above, the aperture stop moves on the same orbit as the 3 rd lens group at the time of magnification (zooming) from the wide-angle end state to the telephoto end state, but may move on an orbit different from the 3 rd lens group.

In order to reduce glare and ghost and realize high optical performance with high contrast, an antireflection film having high transmittance in a wide wavelength region may be applied to each lens surface.

The zoom lens according to the present embodiment has a zoom ratio of about 50 to 70.

The zoom lens according to the present embodiment is used for a digital still camera, but is not limited thereto, and may be used for an optical device such as a digital video camera.

Description of the reference symbols

CAM digital static camera (optical equipment)

ZL zoom lens

G1 lens group 1

G2 lens group 2

G3 lens group 3

G4 lens group 4

G5 lens group 5

S aperture diaphragm

And (I) an image surface.

Claims (7)

1. A zoom lens, characterized in that,

comprising a 1 st lens group having positive power, a2 nd lens group having negative power, a 3 rd lens group having positive power, a 4 th lens group having negative power, and a 5 th lens group having positive power, which are arranged in this order from the object side along the optical axis, and consisting essentially of five lens groups,

the 1 st lens group, the 2 nd lens group, the 3 rd lens group, the 4 th lens group, and the 5 th lens group move along an optical axis in such a manner that an interval between the 1 st lens group and the 2 nd lens group, an interval between the 2 nd lens group and the 3 rd lens group, an interval between the 3 rd lens group and the 4 th lens group, and an interval between the 4 th lens group and the 5 th lens group respectively vary upon varying magnification from a wide-angle end state to a telephoto end state,

the 2 nd lens group is composed of a 1 st negative lens, a2 nd negative lens, a positive lens and a 3 rd negative lens arranged in order from the object side along the optical axis,

the positive lens and the 3 rd negative lens are joined,

and satisfies the following conditional expressions:

-0.180<(f1×fw)/(f2×ft)<-0.160

wherein,

fw: a focal length in a wide-angle end state of the zoom lens,

ft: a focal length of the zoom lens in a far-focus end state,

f 1: a focal length of the 1 st lens group,

f 2: focal length of the 2 nd lens group.

2. The zoom lens according to claim 1,

the following conditional expressions are satisfied:

-0.180<f4/ft<-0.140

wherein,

ft: a focal length of the zoom lens in a far-focus end state,

f 4: focal length of the 4 th lens group.

3. The zoom lens according to claim 1,

the 4 th lens group is composed of a cemented lens of one positive lens and one negative lens.

4. An optical apparatus has a zoom lens for imaging an image of an object on a predetermined surface,

the zoom lens is the zoom lens according to claim 1.

5. A zoom lens, characterized in that,

comprising a 1 st lens group having positive power, a2 nd lens group having negative power, a 3 rd lens group having positive power, a 4 th lens group having negative power, and a 5 th lens group having positive power, which are arranged in this order from the object side along the optical axis, and consisting essentially of five lens groups,

the 1 st lens group, the 2 nd lens group, the 3 rd lens group, the 4 th lens group, and the 5 th lens group move along an optical axis in such a manner that an interval between the 1 st lens group and the 2 nd lens group, an interval between the 2 nd lens group and the 3 rd lens group, an interval between the 3 rd lens group and the 4 th lens group, and an interval between the 4 th lens group and the 5 th lens group respectively vary upon varying magnification from a wide-angle end state to a telephoto end state,

and satisfies the following conditional expressions:

-0.90<f2/TL2<-0.60

-0.180<f4/ft<-0.140

-0.180<(f1×fw)/(f2×ft)<-0.160

wherein,

f 1: a focal length of the 1 st lens group,

f 2: a focal length of the 2 nd lens group,

TL 2: a length on the optical axis of the 2 nd lens group,

f 4: a focal length of the 4 th lens group,

ft: a focal length of the zoom lens in a far-focus end state,

fw: a focal length of the zoom lens in a wide-angle end state.

6. The zoom lens according to claim 5,

the 4 th lens group is composed of a cemented lens of one positive lens and one negative lens.

7. An optical apparatus having a zoom lens for imaging an image of an object on a predetermined surface,

the zoom lens is the zoom lens according to claim 5.

Images